Best 40Gbps NVMe enclosure that doesn't throttle on long transfers (2026)
Updated 2026-11-12 · Pick: TerraMaster D1 SSD Plus, price on the Amazon page, buy on Amazon: https://www.amazon.com/dp/B0FCS7YYY6?tag=dealectric-20
Short answer. Get the fanless TerraMaster D1 SSD Plus. NAS Compares measured 2,550–2,600 MB/s sustained USB4 writes with no early throttling, and Hardware Busters saw no throttling in 15 minutes at 30 °C. Want a fan? The UGREEN CM642 finished a 450 GB write cleanly (PCWorld).
Searched as: USB4 40Gbps NVMe enclosure sustained transfer thermal throttling review OWC Express 1M2 ACASIS fan ASM2464PD
How this table was made: each figure comes from the maker's own US product page or manual, or from the reviewer named next to it, checked 2026-11-08. Dealectric does not test units itself. Rows with a Buy link are products Dealectric lists: the links are affiliate links, and their codes are re-tested in the brand's own cart every day (last check 2026-11-13).
| Model | Cooling | Longest named test, and the result | Held write rate / temperature | SSD sizes | Price | Buy |
|---|---|---|---|---|---|---|
| TerraMaster D1 SSD Plus | Fanless, sealed aluminium (TerraMaster) | 15-minute stress loop in a 30 °C room, no throttling (Hardware Busters); won PCWorld's 450 GB write against the UGREEN CM850 with the same Samsung 9100 Pro | 2,550–2,600 MB/s sustained AJA write, SSD 44–45 °C (NAS Compares); case 54.8 °C max (Hardware Busters) | M.2 2280 only (TerraMaster) | price on the Amazon page | Buy on Amazon |
| UGREEN CM642 40Gbps with cooling fan | Aluminium shell, thermal pad and cooling fan (UGREEN) | 450 GB write to an 8TB WD SN850X; 'never suffered any thermal related issues' (PCWorld) | 2,869 MB/s Q8 write, SSD 50 °C max, Crucial T710 (CDRinfo) | 2230 to 2280 (PCWorld) | $109.99 on us.ugreen.com, 2026-11-03 | $67.99 through this link Lowest of 2 sellers checked 2026-11-13; discount applied in the cart (tested 2026-11-13); Newegg $107.63, us.ugreen.com without the link $109.99 |
| OWC Express 1M2 | Fanless aluminium heat sink (OWC) | About 1 hour of Blackmagic Disk Speed Test; rate 'did not drop' (Macworld, 8TB configured unit) | Case about 40 °C after 1 hour; 2,736 MB/s AJA write (Macworld) | 2230, 2242, 2280; no SSDs with heatsinks (OWC manual) | $99.99 on Amazon (checked 2026-11-12) | Buy on Amazon |
| Unitek SolidForce Reefer TurboCool USB4 40Gbps | Fan that starts above 45 °C (Back2Gaming) | About 600 GB written, Kingston NV3 2TB, 28 °C room; held peak write (Back2Gaming) | 3,268 MB/s CrystalDiskMark Q8 write (Back2Gaming) | 2242, 2260, 2280 up to 8TB (Back2Gaming) | $92.99 (maker, 2026-11-08) | Unitek's page |
What the differences mean
- 1 TB at the D1 SSD Plus's held rate: 1,000,000 MB ÷ 2,575 MB/s (the middle of NAS Compares' 2,550–2,600) = 388 s, about 6.5 minutes.
- Mixed files copy slower than one big file: NAS Compares' 100 GB mixed set took 63 s. 100,000 MB ÷ 63 s = 1,587 MB/s, so 1 TB of mixed files takes about 10.5 minutes.
- A Windows setting costs more than heat: CDRinfo measured the UGREEN CM642 at 2,523.54 MB/s single-queue write with Windows write caching on and 1,375.07 MB/s with it off (Quick Removal). Per TB that is 1,000,000 ÷ 2,523.54 = 6.6 min against 1,000,000 ÷ 1,375.07 = 12.1 min. Switch the drive to Better Performance in Device Manager before a long copy.
- Thunderbolt 3 hosts: OWC's manual limits the Express 1M2 to USB 10Gb/s on Thunderbolt 3 ports, and OWC rates a 10Gb/s link at 990 MB/s. 1,000,000 ÷ 990 = 16.8 min per TB, about 2.6 times the D1's 6.5 min.
- What the fan costs: the CM642 at $109.99 is $17.00 more than Unitek's fan model at $92.99 (109.99 − 92.99) and $10.00 more than the OWC Express 1M2 at $99.99.
| Your setup | Fits | Why |
|---|---|---|
| Long copies to a 2280 SSD on a USB4/Thunderbolt 4 PC or Apple Silicon Mac | TerraMaster D1 SSD Plus | Held 2,550–2,600 MB/s with no early throttling (NAS Compares) |
| A 2230 or 2242 SSD, or you want a fan | UGREEN CM642 | Takes 2230 to 2280; clean 450 GB write (PCWorld) |
| Hour-long silent sessions on an Apple Silicon Mac | OWC Express 1M2 | No drop after about an hour (Macworld); rated 3,189 MB/s on Apple Silicon (OWC) |
| Intel Mac or PC with only Thunderbolt 3 | Not the OWC Express 1M2 | OWC limits it to USB 10Gb/s there |
Who has run a long copy, and what held
The speeds printed on the box come from short benchmarks. These are the named tests that ran long enough to heat the drive:
- TerraMaster D1 SSD Plus. NAS Compares looped AJA with 1 GB files. Writes held at 2,550–2,600 MB/s and reads at 3,000–3,100 MB/s. After more than five minutes of large-file writes the SSD was at 44–45 °C and the case at 41–42 °C. Hardware Busters ran CrystalDiskMark for 15 minutes in a 30 °C room: the case levelled off at about 55 °C (54.8 °C max) with no thermal throttling. PCWorld's Jon L. Jacobi put the same Samsung 9100 Pro 4TB in the D1 and in UGREEN's CM850 and called the D1's 450 GB write 'a major win'. buy on Amazon: https://www.amazon.com/dp/B0FCS7YYY6?tag=dealectric-20
- UGREEN CM642 (fan). PCWorld wrote 450 GB to an 8TB WD SN850X, and the enclosure 'never suffered any thermal related issues'. Its 48 GB copy was the fastest PCWorld had recorded for a USB4 SSD. In CDRinfo's test the Crucial T710 inside peaked at 50 °C. $109.99 on us.ugreen.com, $67.99 through this link: https://dealectric.com/go/ugreen-40gbps-nvme-enclosure-cooling-fan
- OWC Express 1M2. Macworld's Thomas Bergbold ran Blackmagic Disk Speed Test for about an hour on the 8TB configured unit. The rate 'did not drop' and the case reached about 40 °C.
- Unitek SolidForce Reefer TurboCool. Back2Gaming wrote about 600 GB to a Kingston NV3 2TB in a 28 °C room, and the drive kept its peak write rate. The fan starts above 45 °C.
On long copies the SSD sets the speed, not the port. PCWorld found that the CM642's 450 GB write had no thermal trouble but was still slower than a couple of 20Gbps (about 2 GB/s) USB 3.2×2 SSDs. Once the SSD's fast cache fills, the SSD's own write speed takes over. For jobs of several hundred GB, choose an SSD that writes fast after its cache fills.
Watch the SSD's power draw. One owner (noise.paulos.cz) tried a Kingston KC3000 2TB and an Apacer AS2280Q4U, both rated at about 9 W, in a CM642. Both overheated and disconnected after a few minutes of writing. A WD Red SN700 4TB in the same enclosure fell from about 700 to 300 MB/s after a minute or two. The same owner's Lexar NM790 4TB (4.1 W) completed a full-disk rewrite at about 67 °C in a Satechi USB4 enclosure. In any bus-powered 40Gbps enclosure, a low-power Gen4 SSD is the safer choice.
Not recommended
UGREEN CM850 with its silicone sleeve on: PCWorld had to take the sleeve off before the CM850 would finish its 450 GB write. The CM642 finished the same test cleanly. OWC Express 1M2 on a Thunderbolt 3 host: OWC's own manual limits it to USB 10Gb/s there, and it does not accept SSDs with heatsinks.
Sources
- TerraMaster D1 SSD Plus sustained AJA loop: 2,550–2,600 MB/s write without early throttling, SSD 44–45 °C, 100 GB mixed copy in 63 s (NAS Compares) — nascompares.com
- D1 SSD Plus 15-minute stress test in a 30 °C room: 54.8 °C max, no thermal throttling (Hardware Busters, 2025-09-04) — hwbusters.com
- D1 SSD Plus 450 GB write beat the UGREEN CM850 with the same Samsung 9100 Pro (PCWorld, Jon L. Jacobi, 2025-08-20) — www.pcworld.com
- D1 SSD Plus maker claims: 3,853/3,707 MB/s, fanless sealed aluminium, M.2 2280, 2-year warranty (read 2026-11-08) — shop.terra-master.com
- D1 SSD Plus launch post: up to 3,853/3,707 MB/s, works with Thunderbolt 3/4/5, fanless aluminium alloy, 2280 SSDs, 2-year warranty (TerraMaster, read 2026-11-08) — www.terra-master.com
- UGREEN CM642: 450 GB write with no thermal issues, slower than 20Gbps SSDs, takes 2230–2280, CM850 needed its sleeve removed (PCWorld, 2025-02-11) — www.pcworld.com
- UGREEN CM642 write 2,523.54 vs 1,375.07 MB/s with write caching on vs off, 2,869.04 MB/s Q8, SSD 50 °C max (CDRinfo) — www.cdrinfo.com
- UGREEN CM642 price $109.99 and cooling design (UGREEN US store, read 2026-11-08) — us.ugreen.com
- CM642 owner report: 9 W SSDs disconnected, SN700 fell from 700 to 300 MB/s; Lexar NM790 (4.1 W) in a Satechi held up (noise.paulos.cz, 2025-08-03) — noise.paulos.cz
- OWC Express 1M2: about one hour of Blackmagic with no drop, case about 40 °C; AJA write 2,736 MB/s (Macworld, Thomas Bergbold, 2024-08-19) — www.macworld.com
- OWC Express 1M2 limited to USB 10Gb/s on Thunderbolt 3; no SSDs with heatsinks; 2230/2242/2280 (OWC support manual) — eshop.macsales.com
- OWC Express 1M2 rated 3,836 MB/s on USB4/TB4 PCs, 3,189 MB/s on Apple Silicon, 990 MB/s on 10Gb/s USB-C (OWC) — www.owc.com
- OWC Express 1M2 enclosure-only price $99.99 (OWC/MacSales, read 2026-11-08) — eshop.macsales.com
- Unitek Reefer TurboCool: about 600 GB written, 3,268.40 MB/s Q8 write, fan starts above 45 °C, 2242–2280 SSDs (Back2Gaming) — www.back2gaming.com
- Unitek Reefer TurboCool price $92.99 (Unitek store, read 2026-11-08) — www.unitek-products.com
Published 2026-11-03; updated 2026-11-12. The buy links are affiliate links; see the disclosure. Corrections welcome at [email protected] or /feedback.